The present invention relates to a method of terminating an annularly corrugated metal tube that is covered with a braided wire shroud.
Corrugated and convoluted metal tubes are often covered by braided wire shrouds to increase the tube burst strength when used to convey high pressure fluids. Such tubes are frequently welded to end fittings by which they can be detachably coupled to fluid handling equipment. Sometimes the tubes are welded directly to the fluid handling equipment. In either case, the tube termination must be formed by cutting off both the braided shroud and the corrugated metal tube.
Annularly corrugated metal tubes are often preferable to helically convoluted tubes because of improved performance in high pressure applications. Among other things, annularly corrugated tubes can be joined hermetically to fittings more easily than helically corrugated tubes because the tube termination can form a regular circular configuration wherever the tube is cut-off in a plane that is normal to the tube axis. The tubes are usually sawed to form the termination. Most fittings are designed to join the tube to the fitting at the radially inner valley of a corrugation.
When used in pressure applications, annularly corrugated tubes are covered by a braided wire shroud that extends completely along the tube length and is fixed in the fitting, or the like, with the tube end. Because the shrouds are tightly braided, the tube can not be seen as the braid and tube are cut off. Accordingly, the tube is often cut off at a location that is spaced longitudinally from the radially inner valley of a corrugation or any other tube location where the termination is desired. This necessitates grinding the tube end until the tube terminates at the radially inner valley of a corrugation, or otherwise at a desired location. The grinding operation is not only time consuming and labor intensive but also leaves the braided shroud end badly frazzled. Welding the shroud end to the tube is complicated by the frayed shroud end.
The present invention provides a new and improved method of terminating an annularly corrugated metal tube covered by a braided wire shroud wherein the tube is accurately cut-off where desired without the necessity of grinding the tube end and shroud.
The present invention concerns a method of making a wire braid shrouded annularly corrugated metal tube. An annularly corrugated metal tube is formed with corrugations having radially inner corrugation valleys and radially outer corrugation peaks. Adjacent corrugation peaks and valleys are connected by generally radially extending tube wall sections. A braided wire shroud is placed around the corrugated tube with the shroud extending along the radially outer corrugation peaks. A forming tool is moved into engagement with the braided shroud to yieldably deform a portion of braided shroud and move the deformed portion substantially into conformity with a tube corrugation valley so that the valley is located. The shroud also conforms to the corrugation peaks on opposite sides of the located tube corrugation valley during the deformation process. The braided shroud and tube are then severed.
In the illustrated embodiment of the invention the shroud obscures the tube from view. The forming tool is guided by engagement with the shroud and the underlying tube wall into the corrugation valley to locate the valley and the adjacent peaks along the shrouded tube. The illustrated forming tool is rotated relative to the corrugated tube as the forming tool moves radially inwardly so the shroud is deformed into the tube corrugation valley around the tube circumference.
The shrouded tubed is severed by a second tool. In the illustrated and described embodiment of the invention the shroud and tube are severed between the corrugation peaks on opposite sides of the valley by a cutting tool that rotates relative to the shrouded tube.
Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description in connection with the accompanying drawings.